Torque-limiting wrench



TRQUE-LIMTHNG WRENCH Robert Glen Woods, South Gate, Salif., assignor tollo-Line Tools lne., South Gate, Calif., a corporation of CaliforniaApplication September 7, 1954, Serial No. 454,459

6 Claims. (Cl. Slm-52.4)

The present invention relates generally to wrenches and moreparticularly to a novel torque wrench.

Modernly, torque-limiting wrenches find wide application in manyindustries. Generally, these torque-limiting wrenches include aload-engaging member and a spring which resists the movement of theload-engaging member until the desired limited amount of torque isapplied to the load thereby. The application of such limited amount oftorque to the load through the load-engaging member causes the latter toundergo movement from its original position against the force of thespring. Such movement provides an indication that the desired limitedamount .of torque has been applied to the load. In certain industries itis desirable that a single torque wrench be capable of applying a firstlimited amount of torque when moved in one direction and a secondlimited amount of torque when moved in the opposite direction.

It is a major object of the present invention to provide a novel torquewrench which will apply a first limited amount of torque when moved inone direction and a second limited amount of torque when moved in theopposite direction.

Another object is to provide a torque wrench of the aforedescribednature wherein the amount of torque applied by said wrench when moved ineither direction may be adjusted.

A further object is to provide a torque wrench which is very accurate.

An additional object is to provide a torque wrench of compact size andlight weight that is economical of construction.

Yet a further object of the invention is to provide a torque wrench thatis simple of design and rugged of construction whereby it may afford along service life.

These and other objects and advantages of the present invention willbecome apparent from the following detailed description of a preferredembodiment thereof, when taken in conjunction with the appended drawingswherein:

Figure l is a top view of a torque wrench embodying the presentinvention, which view is partly broken away in horizontal section;

Figure 2 is a fragmentary, central vertical sectional view of the frontportion of said wrench;

Figure 3 and 4 are enlarged fragmentary horizontal sectional viewsshowing the mode of operation of said wrench; and

Figure 5 is a diagrammetric view showing the force conditions arisingduring operation of said torque wrench.

Referring to the drawings, the preferred form of torque wrench embodyingthe present invention broadly comprises a head H; a tubular body Bextending away from the rear of the head; a tubular handle T extendingaway from the rear of the body; a plunger P longitudinally slidablydisposed within the front portion of the body B; a `spring S thatconstantly biases the plunger forwardly toward the head; and a shortpivot L interposed between rates arent O fice the rear of the head andthe front of the plunger. The front portion of the head Hy is formedwith a loadengaging member 1li. Torque may be applied to an objectthrough the load-engaging member 10 by moving the handle T in either aclockwise or a counter-clockwise direction from its position of Figurel.

More particularly, the head H is pivotally connected to the front of thebody B by a vertical pivot pin 12 having its ends disposed withinaligned bores 14 and 16 formed in the body and its intermediate portiondisposed within a bore 17 that extends through the head. A rubbersealing ring 18 is positioned in the annular space between the outerperiphery of the head and the inner periphery of the body B. Theload-engaging member 10 may be integral wtih the front of the head anddepends therefrom for engaging a socket of an object to which a load isto be applied (not shown). The load-engaging member 10 is shown as beingrectangular in cross-section. It will be understood, however, that thisload-engaging member may assume other forms without departing from thespirit of the present invention. lt should be further understood thatalthough the load-engaging member l@ is shown disposed axially forwardlyof the pivot pin 1:2, it is possible to arrange this member in alignmentwith the pivot pin without departing from the spirit of the presentinvention.

The rear portion oi' the head H is integrally formed with a hingeelement 22 that may be smaller in diameter than the main portion of thehead. The rear end of this hinge element 22 is centrally formed with aforwardly extending depression 24, the sides of which are beveled asindicated at 26. The front end of the pivot L is disposed within thedepression Z4 of the hinge element 22. The plunger P is of circularcross-section having an outside diameter somewhat smaller than theinside diameter of the body B. rihe front end of this plunger iscentrally formed with a rearwardly extending depression 23. This:depression 2S is generally triangular in plan view having a long side 30and a shorter side 32. The rear end 34. of the pivot L is beveledrelative to its sides and normally abuts the longer side 30 of thedepression 23, as shown in Figure l.

The spring S is of the helical compression type and its rear end abuts acircular plug 36. This plug 36 in turn abuts the front of the handle T.A locking sleeve 38 is suitably journaled by the rear end of the body B,which locking sleeve is threadably engaged with threads 40 formed on thefront portion of the handle T. A lock ring 42 is threadably engaged withthreads d4 formed on the rear portion of the body B. With thisarrangement, the handle T may be adjusted longitudinally relative to thebody B and the forwardly directed force exerted on the spring S againstthe rear of the plunger l may thereby be adjusted. The handle T may belocked relative to the body B by tightening the lock ring 42 against thefront of the locking sleeve 38. In order to provide a visual indicationof the relative positions of the handle T and the body B, the lockingsleeve 38 may be marked with sealer markings 39 adapted to be utilizedin conjunction with complementary Scaler markings 41 formed on thehandle. These markings 39 and 41 may constitute Vernier graduationsreading in foot-pounds or inch-pounds and should be so coordinated withthe spring rate of the spring S and the geometry of the wrench as toprovide an indication of the amount of torque applied by theload-engaging member lt).

In operation, referring to Figures l and 3, and assuming that theload'engaging member 10 has been connected with a load, the rear end ofthe handle T is moved in a clockwise direction. During such movement thetendency of the head H to pivot in a counter-clockwise directionrelative to the body B will be resisted by the spring S, such resistancebeing applied through the plunger P and the 'pivot L. When, however, thetorque being applied by the load-,engaging member reaches apredetermined limited magnitude the head H will break or pivot in acounterclockwise direction about the pivot pin 12, the pivot L pivotingwithin .the .depressions 24 and 28 as shown in Figure 3. rlThe abutmentof the hinge element 22 4with the `interior of Vthe body B at points 46may limit the amount of pivotal movement which may be undergone by thehead. it should be noted that the pivot L pivots on a knife edge whenthe head break and accordingly .only a minimum amount of friction willbe developed between the front and rear ends of the pivot L and the'hinge and plunger elements.

Referring now to Figure 4 it it is desired to apply a limited amount oftorque in the .opposite direction, the rear end ef the handle T is movedin a .counter-clockwise direction. When the torque being applied by theload-y engaging member reaches a second predetermined limited magnitude,the head H will break `or pivot in a clockwise .direction about thepivot pin 12, the pivot L pivoting within the depressions 24 and 28, asshown in Figure 4. in this case the abutment of the hinge element 22with the interior of the body at points 50 may be utilized to limit theamount of pivotal movement which may be undergone by the head H.

It ,should be particularly observed that the limited amount of torquerequired to `cause the head H to break to its position of Figure 3 is ofa smaller magnitude than that required to cause it to break to itsposition of Figure 4. The reasonfor this will become apparent fromexamination of Figure 5, which ligure is a diagrametric yor vectorialrepresentation of the forces involved in the pivotal movement of thehead H relative to the other ele-ments of `,the wrench. in Figure 5, theline ab represents a base line followed by the rear end of the head H asit breaks in either direction. it likewise represents the amount offorce available at the rear end of the head during a breaking movementfor urging the plunger P rearward-1y against the force of the spring S.The line b--c represents the direction of the force being transferredfrom the head H to the plunger P during clockwise rotation of the handleT about the pivot l2. Likewise, the

line a-cl represents the direction of the force actually transferredfrom the head H to the plunger P during a counter-clockwise rotation ofthe handle T about the pivot 12. VThe actual magnitude of the rearwardlyacting force exerted by the head H upon the plunger P during clockwiseand counter-clockwise, respectively, movement-s of the handle T isrepresented by lines a-c and b-a.', respectively. inasmuch as line 1--0is longer than line b--fL the magnitude of the rearward force exertedagainst the plunger P by the head H during said clockwise rotation isgreater than that exerted against the plunger during saidcounter-clockwise rotation for any given force directed along line awt).Accordingly, since the forwardly acting force applied by the spring Sagainst the plunger P is constant, the limited amount of torque requiredto be exerted by the wrench upon a load in order to cause the head H tobreak to its position of Figure 3 is less than that required to causethe head to break to its position of Figure 4.

While there has been shown and described hereinbefore what is presentlyconsidered the preferred embodiment of the present invention, it will beapparent that various modilicationsand changes may be made theretowithout departing from the spirit of the invention or the scope of lthefollowing claims.

l claim:

l. A torque-limiting wrench, comprising: an elongated handle; a headmember pivotally secured to the front portion of said handle, said headbeing formed with loadengaging means; a plunger member axially slidablycarried by said handle rearwardly of said head and axially spacedtherefrom; resilient means interposed between said handle and saidplunger member for constantly urging the latter forwardly toward saidhead; and, a pivot element interposed between .the .rear of .said headmember and the front of said plunger member, one end of said pivotelement being beveled relative to its sides and the member adjacent saidbeveled end being formed with a complementary depression for receivingsaid beveled end.

2. A wrench as set forth in claim l where said resilient means includesspring means.

3. A wrench as set forth in claim 2 which includes means for adjustingthe effective force exerted by said spring means. Y

4. A torque-limiting wrench, comprising: an elongated handle; a headmember pivotally secured to the front portion ofV said handle, said headbeing formed with load-engaging means; a plunger member axially slidablycarried by said handle rearwardly of said head and axially spacedtherefrom; and, a pivot element interposed between the rea-r of saidhead member and the front 4.of said plunger member, `the rear end ofsaid pivot element being beveled relative to its sides and the front ofsaid plunger member being formed with a complementary triangulardepression for receiving the rear end of said pivot.

5. A torquedimiting wrench, comprising: a tubular body; a head memberpivotally secured to the front portion of said body, said head memberbeing formed lwith loadfenga-ging means; a plunger member axiallyslidably disposed within said body rearwardly of said head mem.- ber andaxially spaced therefrom; spring means in said body rearwardly of saidplunger member for biasing Vthe latter forwardly toward said head; ahandle extending from the rear of said body; and, a pivot elementinterposed between the rear of said head member and the front ,of ,saidplunger member, the rear end of said pivot element being beveledrelative to its sides, the front of said plunger member being formedwith a complementary triangular rearwardly extending depression forreceiving the read end of said pivot element, and the rear of said headmember being formed with a forwardly extending depression for receivingthe front end of said pivot element.

6. A torque-limiting wrench, comprising: a tubular body; a head memberpivotally secured to the front portion of said body, said head memberbeing formed with loadengaging means; a plunger member axially slidablydisposed within said body rearwardly of said head member and axiallyspaced therefrom; a tubular handle telescopically extending from therear of said body; a circular plugv at the front end of said handle; ahelical compression spring interposed between said plug and the rear ofsaid plunger member; threads formed on .the outer rear surface of saidbody and the outer front surface of said handle; a locking sleevejournaled by the rear of said body and formed with threads that areengaged with the threads of said handle; a lock ring disposed forwardlyof said locking sleeve and formed with threads that are engaged with thethreads of said body; and, a pivot element interposed between the rearof said head member and the front of said plunger member, the rear endo-f said pivot element being beveled relative to its sides, the front ofsaid plunger member being formed with a complementary triangularrearwardly extending depression for receiving the rear end of -saidpivot element, and the rear of said head member being formed with aforwardly extending depression for receiving the front end o-f Asaidpivot element.

References Cited in the tile of this patent UNITED STATES PATENTS2,172,561 Kruse Sept. l2, 1939 2,365,486 Morris Dec. 19, 1944 2,595,274Latimer May 6, -2l 2,662,436 Harmes Dec. 15, 1953 2,667,809 .GarwoodFeb. 2, 1954

